Molecular Dynamics Simulation of Aqueous Sodium Chloride Solution at the NaCl(001) Interface with a Polarizable Water Model

Abstract

The sodium chloride solution−NaCl crystal interface serves as an example of aqueous electrolytes at uncharged ionic surfaces and plays an important role in technologically relevant processes and atmospheric chemistry. This interface is investigated by classical molecular dynamics simulations at ambient pressure and generally at 298 K. A fluctuating charges version of the extended simple point charge (SPC/E) water model, the SPC/E-P model, is used to calculate structural and dynamical properties of the ions at the interface and in the bulk solution: density profiles and potentials of mean force including concentration and temperature dependencies, hydration numbers, lateral structures, and mobilities of ions parallel and perpendicular to the interface. We find that sodium ions are adsorbed selectively at the metastable NaCl(001) interface, and their mobility is strongly reduced due to adsorption. Analogous calculations using the nonpolarizable SPC/E model do not exhibit such an intense exothermic sodium ion adsorption; i.e., solvent polarization can significantly affect ionic distributions close to polar but uncharged interfaces. In the case of SPC/E-P water, dipole moment profiles are calculated also.

Water uptake coefficients and deliquescence of NaCl nanoparticles at atmospheric relative humidities from molecular dynamics simulations

“…48 Several successful models for determining the physical structure and properties of ionic solutions exist in this rapidly expanding field. 20,[49][50][51][52][53] To our knowledge, these models deal with bulk solutions and have not been applied to adsorbed layers. Figure 9 illustrates the RDFs for Na-O and O-O which characterize the solution layer, both of which are inconsistent with the forms expected from literature.…”

“…Molecular dynamics ͑MD͒ simulations provide an ideal tool to investigate the initial stages of water uptake by nanoparticles. Extensive computational work has focused on the interactions of NaCl with water, [18][19][20][21] and both bulk physical and thermodynamic properties have been accurately reproduced from the optimized potentials. Recent work has been successful in modeling water uptake from the vapor phase [22][23][24][25] but has used physical conditions not relevant to the atmosphere.…”

Void-induced dissolution in molecular dynamics simulations of NaCl and water

“…18,19 More recently, studies have focused on the interface of solid NaCl and water 20,21 and on NaCl in contact with a supersaturated solution. 22 With the longest computationally reasonable simulation runs, only limited interaction was observed between the liquid and solid phases because the time scales of dissolution and crystallization are expected to drastically exceed the scope of direct simulation. There are therefore few simulation studies available on the kinetic process of dissolution.…”

Effect of Surface Tension from MD Simulations on Size-Dependent Deliquescence of NaCl Nanoparticles

“…Molecular simulation techniques do not suffer from this limitation and provide a convenient methodology to directly study the interfacial profile between two coexisting fluids or between a fluid and an adjacent solid surface (Alejandre et al 1995;Matsumoto and Kataoka 1987;Nicholson and Parsonage 1982;Rowlinson and Widom 1982;Zykova-Timan et al 2005). Computational studies of sodium chloride solutions (Jungwirth and Tobias 2001;Koneshan and Rasaiah 2000;Lisal et al 2005;Lyubartsev and Laaksonen 1996;Ohtaki and Radnal 1993), interfaces between solid NaCl and water (Shinto et al 1998a;Shinto et al 1998b), and NaCl in contact with a supersaturated solution (Oyen and Hentschke 2002) have detailed the effect of number of simulated molecules, range of molecular interaction, various idealized potentials, system geometry, and corrections for long-range interactions on the simulation results. The ready availability of both well-developed simulation techniques and potentials makes MD accurate and efficient for calculating surface tensions in the NaCl-water-air system.…”